It is increasingly being recognized that people with mental retardation are prone to neuropsychiatric problems. Yet to be determined, however, is whether all of the criteria specified in the DSM-IV can be effectively operationalized for this population. The ultimate focus of the proposed project is clinical depression in people with mental retardation and limited language. Certain hallmarks of depression (changes in body weight, sleep problems, psychomotor agitation, etc.) can be detected readily via behavioral observation techniques. However, other hallmarks (e.g., diminished motivation, behavioral impersistence, etc.) are less readily operationalized. The latter problem arises because (1) people with significant mental retardation cannot participate meaningfully in clinical interviews and (2) third-party reports may be of questionable value in operationalizing these more challenging constructs. To address these two problems, we have assembled a battery of behavioral tests that can assess motivation, attention, memory, and executive functioning in children with limited language. Two parallel tracks of research are proposed. In the first track, we will evaluate the degree to which selected aspects of the battery can inform us about the cognitive functioning of children with dual diagnoses of mental retardation and depression who exhibit little or no communicative language. Potentially informative comparisons will be made with functionally matched, nondepressed contrast participants. In the second track, the battery will be administered to higher functioning, verbally more capable children with mental retardation and with or without depression. This parallel work will not only replicate systematically studies of the first track but will also allow us to assess the correlation between test-battery scores and scores from a conventional neuropsychological instnunent (the NEPSY). The proposed project responds to a priority area recently announced jointly by NICHD and NIMH, the psychopathology of mental retardation (PA-01-028). [unreadable] [unreadable]